Scissors gear structure and manufacturing method thereof

Abstract

Disclosed is a scissors gear structure and a method of manufacturing the same, wherein the scissors gear can efficiently remove backlash and prevent noise and vibrations, and wherein the scissors gear has improved mechanical properties including strength and wear resistance. The present invention provides a scissors gear without requiring separate manufacturing of expensive scissors pins which must be forcibly inserted, and without requiring expensive processing such as fine wire cutting to form grooves at both ends of the scissors spring.

What is claimed is: 
     
         1 . A scissors gear structure, comprising:
 a main gear and a sub gear concentrically disposed so as to be rotatable relative to each other;   an scissors spring disposed between the main gear and sub gear that provides an elastic force so that the main gear and the sub gear are rotatable relative to each other; and   a support projection integrally formed on the main gear and the sub gear, the support projection disposed at positions on the main gear and sub gear so as to support the scissors spring.   
     
     
         2 . The scissors gear structure of  claim 1 , wherein the scissors spring is arc-shaped and has two ends. 
     
     
         3 . The scissors gear structure of  claim 1 , wherein each of the two ends of the arc-shaped scissors spring is supported by the support projections on the main gear and the sub gear. 
     
     
         4 . The scissors gear structure of  claim 1 , wherein an end of the scissors spring comprises a planar end having a shape linearly cut in a radial direction of the main gear and the sub gear, and wherein the support projection includes
 a support planar part that provides a planar surface in surface contact with the planar end of the scissors spring, and   a radial control part positioned to limit movement of the end of the scissors spring inward in the radial direction of the main gear and the sub gear.   
     
     
         5 . The scissors gear structure of  claim 1 , wherein an end of the scissors spring comprises a planar end linearly extending in a radial direction of the main gear and the sub gear, and wherein the support projection includes a rectangular recess into which the planar end is inserted so as to form a surface contact condition. 
     
     
         6 . The scissors gear structure of  claim 1 , wherein an end of the scissors spring comprises a convex arc-shaped end, and the support projection includes an arc-shaped recess complementary to the arc-shaped end so as to form a surface contact condition. 
     
     
         7 . The scissors gear structure of  claim 1 , wherein an end of the scissors spring comprises a trapezoidal end which narrows toward a tip thereof, and the support projection includes a trapezoidal recess complementary to the trapezoidal end so as to form a surface contact condition. 
     
     
         8 . The scissors gear structure of  claim 1 , wherein the main gear and the sub gear are formed by subjecting powder comprising about 0.15˜0.25 wt % of carbon (C), about 0.5˜1.5 wt % of molybdenum (Mo), a remainder of iron (Fe), and other optional materials present at less than 1 wt %, to molding, sintering, rolling, and thermal treatment using carburization. 
     
     
         9 . A method of manufacturing a scissors gear, comprising:
 molding powder comprising about 0.15˜0.25 wt % of carbon (C), about 0.5˜1.5 wt % of molybdenum (Mo), a remainder of iron (Fe), and other optional materials at less than 1 wt %, thus forming molded bodies of each of a main gear and a sub gear (S 10 );   sintering the molded bodies, thus forming sintered bodies (S 20 );   rolling the sintered bodies, thus forming rolled bodies wherein a jagged surface thereof is compacted (S 30 ); and   thermally treating the rolled bodies using carburization to increase hardness of the jagged surface, thus forming the main gear and the sub gear (S 40 ).   
     
     
         10 . The method of  claim 9 , wherein the molding (S 10 ) is performed by adding the powder to an upper mold and a lower mold at about 100° C. or higher and compressing the upper mold and lower mold to provide a molded body having a density of about 7.3 g/cc or more. 
     
     
         11 . The method of  claim 9 , wherein the sintering (S 20 ) is performed in a reduced atmosphere at about 1100˜1300° C. for about 30 min to 2 hr. 
     
     
         12 . The method of  claim 9 , wherein the rolling (S 30 ) is performed by cooling the sintered body to about room temperature after sintering (S 20 ), and the rolling (S 30 ) is performed so that a depth of the compacted jagged surface is about 150˜400 μm.